Relationships between highly skilled golfers

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Journal of Sports Sciences

ISSN: 0264-0414 (Print) 1466-447X (Online) Journal homepage: http://www.tandfonline.com/loi/rjsp20

Relationships between highly skilled golfers’ clubhead velocity and force producing capabilities during vertical jumps and an isometric mid-thigh pull Jack E. T. Wells, Andrew C. S. Mitchell, Laura H. Charalambous & Iain M. Fletcher To cite this article: Jack E. T. Wells, Andrew C. S. Mitchell, Laura H. Charalambous & Iain M. Fletcher (2018): Relationships between highly skilled golfers’ clubhead velocity and force producing capabilities during vertical jumps and an isometric mid-thigh pull, Journal of Sports Sciences, DOI: 10.1080/02640414.2018.1423611 To link to this article: https://doi.org/10.1080/02640414.2018.1423611

Published online: 04 Jan 2018.

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JOURNAL OF SPORTS SCIENCES, 2018 https://doi.org/10.1080/02640414.2018.1423611

Relationships between highly skilled golfers’ clubhead velocity and force producing capabilities during vertical jumps and an isometric mid-thigh pull Jack E. T. Wellsa,b, Andrew C. S. Mitchellb, Laura H. Charalambousb and Iain M. Fletcherb a

The Professional Golfers’ Association, National Training Academy, The Belfry, UK; bInstitute for Sport and Physical Activity Research, University of Bedfordshire, Bedford, UK ABSTRACT

ARTICLE HISTORY

Whilst previous research has highlighted significant relationships between golfers’ clubhead velocity (CHV) and their vertical jump height and maximum strength, these field-based protocols were unable to measure the actual vertical ground reaction force (vGRF) variables that may correlate to performance. The aim of this study was to investigate relationships between isometric mid-thigh pull (IMTP), countermovement jump (CMJ), squat jump (SJ) and drop jump (DJ) vGRF variables and CHV in highly skilled golfers. Twenty-seven male category 1 golfers performed IMTP, CMJ, SJ and DJ on a dual force platform. The vertical jumps were used to measure positive impulse during different stretch-shortening cycle velocities, with the IMTP assessing peak force (PF) and rate of force development (RFD). Clubhead velocity was measured using a TrackMan launch monitor at a golf driving range. Pearsons correlation coefficient analyses revealed significant relationships between peak CHV and CMJ positive impulse (r = 0.788, p < 0.001), SJ positive impulse (r = 0.692; p < 0.001), DJ positive impulse (r = 0.561, p < 0.01), PF (r = 0.482, p < 0.01), RFD from 0–150 ms (r = 0.343, p < 0.05) and RFD from 0–200 ms (r = 0.398, p < 0.05). The findings from this investigation indicate strong relationships between vertical ground reaction force variables and clubhead velocity.

Accepted 25 August 2017

Introduction The ability to drive a golf ball over greater distances is considered to be an important factor linked to success within the game of golf (Broadie, 2014). However, extraneous variables such as centeredness of strike, environmental conditions and friction of the landing area can cause error when measuring a golfer’s drive distance. Inextricably linked to increasing drive distance is the notion of developing clubhead velocity (CHV) at the moment of impact between the golf ball and clubhead (Hume, Keogh, & Reid, 2005). Since CHV is not subjected to the extraneous variables associated with drive distance, it is a more robust measure of golfers’ performance. There are a number of ways to increase CHV including technical alterations or advances in equipment (Cochran & Stobbs, 1999). However, over recent years golfers have devoted an increasing amount of time engaging in strength and conditioning interventions due to research highlighting significant improvements in CHV (Doan, Newton, Kwon & Kraemer, 2006) following resistance training (Fletcher & Hartwell, 2004) and the widespread use of resistance training in professional golfers. Research has evidenced that the downswing of highly skilled golfers is initiated from the ground-up (Hume et al., 2005), with energy transferred through the body’s kinetic chain to the clubhead (Nesbit & Serrano, 2005). While a number of studies have assessed the kinematic parameters of the golf swing, there is a paucity of research assessing the relationship between golfers’ CHV and vertical ground reaction forces (vGRF). Despite a CONTACT Jack E. T. Wells

[email protected]

© 2018 Informa UK Limited, trading as Taylor & Francis Group

KEYWORDS

Golf; strength and conditioning; peak force; impulse; stretch-shortening cycle

number of kinetic mechanisms suggested to relate to CHV; including peak force (PF; Doan et al., 2006), rate of force development (RFD; Read & Lloyd, 2014), impulse (Myers, Lephart, Ysai, Smoglia, & Jolly, 2008) and stretch-shortening cycle (SSC) efficiency (Hume et al., 2005), there has been little research exploring relationships between these parameters and CHV. Previous research has utilised one repetition maximum (1-RM) back squats (Hellström, 2008; Parchmann & McBride, 2011) and vertical jump performance (Lewis, Ward, Bishop, Maloney, & Turner, 2016; Read, Lloyd, De Ste Croix, & Oliver, 2013) to explore possible relationships with CHV. While these procedures provide useful field based assessments, they are unable to measure variables such as PF, RFD and impulse, which are obtainable through the use of force platforms. Furthermore, there is also a great degree of technical proficiency required when performing a back squat. One method that has previously been used in research and is suggested to be a valid measure of PF and RFD is an isometric mid-thigh pull (IMTP; Haff, Ruben, Lider, Twine, & Cormie, 2015). To date, there is only one study that has utilised an IMTP to examine the relationship between PF, RFD and CHV, with the authors reporting no significant relationship between these variables (Leary et al., 2012). However this study employed a small sample size (n = 12) and comprised a high degree of variability in participant level (handicap: −14.5 ± 7.3). A SSC is observed when the musculotendinous unit is stretched before shortening rapidly with ideally a small isometric delay between these two actions (Blazevich, 2011). The SSC has been suggested to be a fast or slow action depending

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J. E. T. WELLS ET AL.

on ground contact times (250 ms; Schmidtbleicher, 1992). It is generally accepted that fast SSCs such as drop jumps (DJs) take advantage of series elastic component (SEC) function and stored elastic energy, whereas slower SSCs, such as countermovement jumps (CMJ), draw upon both the contractile element (CE) and SEC (Wilson & Flanagan, 2008). Furthermore, squat jumps (SJs) are often employed to measure the ability of the musculotendinous unit to perform concentric only movements (Kurokawa, Fukunaga, & Fukashiro, 2001). Consequently, jump variations can be employed to establish if a relationship exists between CHV and different lower extremity SSC velocities. One mechanism speculated to relate to golfers’ performance is their ability to generate impulse (force x time) (Myers et al., 2008). Indeed, Keogh, Marnewick, Maulder, Nortje & Hume, (2009) suggested that the ability of a golfer to generate impulse using the lower extremities is a factor likely associated with golfers’ CHV. Given the impulse-momentum relationship, greater force generated over the duration of the downswing will increase the overall momentum (velocity x mass). Since the mass of a golfer remains constant, the change in impulse will lead to an increase in velocity which ideally will be transferred to the clubhead. Since impulse can be measured during different jump variations, these procedures can be used to assess the relationship between CHV and impulse generated during different SSC actions. Impulse generated during vertical jumps measures the ability of the lower body to utilise different SSCs to produce force over a specified time. Golfers who are able to generate greater impulse during slow SSC activities such as a CMJ, may have an athletic advantage if they are able to successfully transfer this to the clubhead. There is no research however, that examines the relationship between these variables. Recent research has found that slow velocity field based measurements such as 1-RM back squat strength has a significant positive relationship with CHV (Hellström, 2008; Parchmann & McBride, 2011). This is interesting since research has identified that the downswing lasts from 230 – 284 ms (Cochran & Stobbs, 1999; Tinmark Hellström, Halvorsen & Thorstensson, 2010). Given that it can take up to 900 ms to reach PF (Blazevich, 2011), there may not be the prerequisite time window during the downswing to achieve this. Consequently it may be more important for golfers to generate force quickly (i.e. faster RFD). By utilising an IMTP, this can directly measure PF and RFD which will help to determine whether it is the magnitude or rate that has the greatest relationship with golfers’ CHV. The aim of this study was to investigate relationships between IMTP, CMJ, SJ and DJ vGRF variables and peak CHV in highly skilled golfers. From the current literature, it is hypothesised that CHV would have a significant positive relationship with each of the vGRF variables.

engaged in an average of 9 hours golf practice per week and had limited experience of resistance training. Participants were injury free, completed a physical activity readiness questionnaire (PAR-Q), attended a familiarisation session and refrained from exercise 48 hours prior to all testing. Ethical approval was granted by the University’s Research Ethics panel.

Methods

Countermovement jumps

Participants

Force platforms were zeroed with the participants standing motionless in their start position. Countermovement jumps started with the participants standing upright before lowering themselves into a self-selected squat depth and immediately jumping as high and as fast as possible on the command “3, 2, 1, jump”.

Twenty-seven right-handed male category-1 (handicap ≤-5) golfers (age: 19 ± 1.45 years, height: 1.81 ± 0.6 m, mass: 74.85 ± 11.28 kg, handicap: −2.7 ± 1.9) were recruited to participate in this study. All participants were experienced golfers,

Experimental trials Laboratory assessment Anthropometric data (height and mass) were recorded. As a warm-up participants performed pulse raisers on a cycle ergometer for 5 minutes at a cadence of 50 rpm with a resistance that yielded an intensity of 90–100 watts. Following this a series of dynamic stretches were performed including clock lunges, overhead squats, gluteal bridges, scapula wall slides, thoracic rotations, internal and external hip rotations and vertical and horizontal arm swings. Each participant received five minutes rest before completing testing of the SJ, followed by CMJs, DJs and lastly the IMTP. All performance tests were performed on dual Kistler force platforms (Kistler 9281, Kistler Instruments, Winterthur, Switzerland) sampling at 2000 Hz.

Vertical jumps All participants were taken through a standardised verbal explanation and demonstration by the investigator. Following this, participants performed three practice trials prior to completing the test procedures. Each vertical jump was performed three times with the feet hip width apart, hands placed on the hips, and with the instruction to jump as high and as fast as possible on the command “3, 2, 1, jump”. Each trial was interspersed with a two minute recovery period.

Squat jumps During practice trials participants set their preferential start position with knee (95 ± 12°) and hip angles (84 ± 18°) recorded using a universal goniometer. An adjustable bench was individually set to each participant’s preferred squat depth to provide a standardised start position. Force plates were zeroed with the participants set motionless in their lowered position of the squat. The participants held their self-selected squat depth for 5 seconds then performed a concentric only jump. All force-time data was analysed on a computer screen, with a negative vGRF >50 N from the force trace deemed as a prior countermovement (Thomas, Jones, Rothwell, Chiang, & Comfort, 2015). If a countermovement was performed the data was discarded and the trial was performed again following the allocated rest intervals.

JOURNAL OF SPORTS SCIENCES

Drop-jumps A 20 cm high box was set back from the force platforms. On the command “3, 2, 1, jump” participants “dropped” from the box into a hip width stance and attempted to jump as high as possible whilst minimising their ground contact time. The experimenter discarded jumps adopting poor technique such as “stepping down” or “jumping” off the box. Jumps with ground contact time >250 ms were also discarded. After completing all the vertical jumps, the athletes rested for five minutes prior to taking part in the IMTP, which follows previous procedures reported by Leary et al. (2012).

Isometric mid-thigh pull All isometric testing was performed using a Smith machine (Pro-R, Pullum Sports, Luton, UK), which was set over the dual Kistler force platform system. Prior to data collection, participants performed three sub-maximal isometric pulls, progressively increasing their lifting intensity. Participants were positioned into their second-pull position of the clean, since this has been shown to correspond to the portion of the clean that generates the highest force output (Garhammer, 1993). From this position knee (144 ± 4°) and hip (150 ± 5°) angles were recorded with a universal goniometer. Participants’ hands were attached to the bar with lifting straps to enable maximal effort, with the bar fixed in position. Once the lifting position had been set, the participants took “slack” out of the bar and remained motionless whilst the force platforms were zeroed. Participants were informed to pull the bar as hard and as fast as possible (Haff et al., 2015). Each pull was initiated after a countdown of “3, 2, 1 pull” with maximal isometric effort applied for five seconds as recommended by Haff et al. (2015). Following each maximal lift, participants sat on a chair, but remained strapped to the bar. This was to maintain a constant hand position between trials. A total of three pulls were performed with three minutes recovery time between each.

Clubhead velocity assessment CHV was measured using a TrackMan 3e launch monitor (Interactive Sports Games, Denmark), as used by Oliver, Horan, Evans, and Keogh (2016). The TrackMan 3e measures CHV at the instantaneous moment prior to impact (TrackMan, 2017), and is reported to repeatedly measure this variable to within ±0.18 m/s of the actual CHV (TrackMan, 2013). Clubhead velocity was measured in a customised driving range bay at the Belfry Golf Centre. The TrackMan was setup based on manufacturer’s guidelines with the investigator specifying the intended target line. The warm-up followed the same procedures used as the laboratory testing. Participants also hit a self-selected number of shots (5 ± 1 shots) with a 6iron whilst gradually increasing their CHV. This was then followed with a self-selected number of shots (6 ± 1 shots) struck with a driver. Participants used their own custom fit 6-iron and driver which comprised either a stiff or X-stiff shaft to ensure shaft flexibility didn’t confound CHV data. Prior to data collection the investigator instructed each participant to ensure they struck the ball with maximum effort, whilst maintaining their normal swing mechanics and a centred strike on the clubface.

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The final two warm-up shots were struck with maximum effort to ensure participants were suitably prepared. Participants self-selected and struck 10 new range balls, aiming at the target and hit off an artificial turf mat and a self-selected tee height. Centeredness of strike was determined by sound, feel and the ball flight, with the investigator checking verbally with the participant after each shot. Any shots that fell outside this remit were discarded and additional shots were performed, up to a maximum of 15 shots.

Data analysis Smoothing and residual analysis All data was smoothed with a low pass 4th order Butterworth filter as described by Winter (2009). Residual analysis was used to determine optimal cut-off frequency (Winter, 2009) which was set at 30 Hz for the IMTP and 100 Hz for all three jump variations (Kawamori, Nosaka, & Newton, 2013). The instant of movement initiation was determined based on a 10 N vGRF threshold shift from baseline measurements as utilised by Tirosh and Sparrow (2003).

Kinetic analysis Peak force during the IMTP was established from the maximal vGRF on the force-time curve subtracted by the lowest starting force. Rate of force development was calculated as the change in force divided by the change in time generated over pre-determined time integrals of 0–50 ms, 0–100 ms, 0–150 ms and 0–200 ms. Positive impulse was calculated from the area underneath the force-time curve for the CMJ and SJ. Drop jump positive impulse was calculated from the vertical force trace including impulse pertaining body mass and force generated through muscular actions.

Clubhead velocity data The TrackMan launch monitor provided real-time biomechanical data on each participant’s CHV for the ten trials. Peak data for CHV and the vGRF variables were taken forward for analysis.

Statistical analysis Within-session reliability was determined using the coefficient of variation (CV) statistic and respective 95% confidence intervals. For each variable, acceptable reliability was determined as a CV

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